264 TAGE SKOGSI!i;R(i 



Still more interesting is the statement about the parasitic occurrence of species of this 

 sub-genus that is given by Ch. B. WILSON, 1913 (a preliminary note 1911, p. 22). This author 

 describes (p. 269) a now species called Cypridina paradtica, which is certainly unidentifiable 

 as a species, but without doubt belongs to the same sub-genuB as does the species that I have 

 dealt with above. This form seems to have been discovered as a parasite in no less than five 

 cases: ,,Five lots of this o s t r a c o d were obtained in all; two of these were taken from the 

 gills of two hammer-head sharks, Sphyrna zycjaena, on July 9, and include about 50 specimens 

 each . . . The third lot contains a single specimen found on the gills of Epinephelus adscensionis, 

 August 9. . . . The fourth lot contains three specimens taken from the gills of a jack, Caranx 

 crysos, August 1. The fifth lot contains 12 specimens and was obtained from the nasal tubes 

 of the hammer-head shark on June 17." 



Whether all these finds given by Wilson really refer to a single species is anything but 

 certain, at least if we are to judge from the superficial way in which the species in question is 

 described and reproduced. A comparison between the two reproductions of the furca given 

 in pi. 53, figs. 303 and 311 is even decidedly against such an assumption. 



On the same page on which this information is found WiLSON gives the following details 

 about these finds. „That the presence of these o s t r a cods on the fishes' gills was not 

 accidental is abundantly proven by the following considerations: First there were too many 

 of them; one or two or half a dozen might be washed on to the gills of a fish accidentally, 

 but not 40 or 50. Again they were arranged altogether too regularly; in the space between 

 the bases of two adjacent filaments and in contact with the gill arch, there was always a single 

 o s t r a c o d, its long diameter at right angles to the gill arch, so that its anterior end 

 projected slightly on one side between the filaments, and its posterior end on the other side. — 

 Furthermore the tissues of each filament where they came in contact with the shell of the 

 s t r a c o d, were hollowed out in the center and slightly raised around the edges, thus forming 

 a sort of pocket, which held the o s t r a c o d securely in place so that it could be removed 

 only with a pair of forceps. This of course is absolute proof that the ostracod was not 

 washed in temporarily, but that it had remained in position long enough to produce this effect 

 on the tissues. In view of such conditions these o s t r a c o d s may fairly be called parasitic. 

 While it is impossible to see how ttey can draw any blood from the fish's gills, yet they certainly 

 share the oxygenated water with which the fish keeps its gills supplied, and they get their food 

 in some way while there. For food they may devour anything that the water contains and 

 brings to them, they may eat scraps of the fish's food that come their way, or they may feed 

 on the slime with which the fish's gills are covered. It is impossible to determine at present 

 just what does constitute their diet." 



No adaptation for parasitism of one kind or the other can be discovered in the 

 form in question — at least if we arc to judge from Wilson's description and figures; on the 

 contrary this species must be said to have the structure that is typical for free-living forms 

 of this genus. Accordingly it seems to me doubtful whether we are concerned in this case, 

 contrary to the 1 wo preceding ones, with a (or several) e x c 1 u s i v e 1 y parasitic form 

 or forms. 



